DESCRIPTION: (Applicant's Description) Human herpesvirus 8 (HHV8) DNA has recently been identified in virtually all biopsies of Kaposi's sarcoma (KS). Only some patients with KS respond to therapy and complete remission is almost never achieved in patients with HIV infection. HHV8 in the peripheral blood of patients with KS in detectable years prior to the development of overt KS, suggesting that HHV8 has a primary role in the development of KS. Differences in HHV8 viral load may explain or predict the range of clinical outcomes seen in patients with KS but this is unknown at present. The investigator's long-term objective is to test the hypothesis that HHV8 viral load is an important variable in the progression and therapeutic response of KS. Their immediate objective is to test the hypothesis that biologically relevant changes in the quantity of circulating HHV8 will be detectable and to measure those changes. Their specific aims are: Specific Aim 1. To determine the optimal collection method for detecting HHV8 in the peripheral circulation. They will use a double nested HHV8 PCR to HHV8 in whole blood plasma, peripheral blood mononuclear cells, and serum collected from HIV-infected patients with KS. Specific Aim 2. To determine the sample, biologic, intra- and inter-patient variability in circulating HHV8 viral load in patients with KS. The investigators will use quantitative PCR to measure the virus copy number in the fraction of blood which has the most readily detectable amounts of HHV8 DNA as determined in specific aim one. Patients will be assessed at 4 to 6 month intervals over a period of 1.5 to 2 years. Clinical KS will be scored using standard assessment tools. They will determine the HHV8 copy number in duplicate samples, in repeated assays and in samples collected days versus months apart. This information will be used to design a large scale trial in which differences in viral load as it relates to clinical disease activity will be determined.